Role of PDZK1 in lipid metabolism and atherosclerosis

衔接蛋白、锚定蛋白和支架蛋白在信号转导中起重要作用。在许多 在某些情况下，信号蛋白之间的相互作用是由小氨基酸序列介导的， 特异性蛋白质结构域，如src同源性（SH）、pTyr结合（PTB）或PDZ结构域。这些相互作用 负责决定受体和转运蛋白的位置、功能和活性， 他人几年前，我们分离出一种新的蛋白质，我们命名为PDZK 1。PDZK 1包含四个PDZ 蛋白质相互作用结构域和相互作用的羧基末端部分的一些膜 相关蛋白包括高密度脂蛋白（HDL）清道夫受体SR-BI和几种离子 通道，其中之一涉及多药耐药性。因此，PDZK 1可能在以下方面发挥重要作用 生物过程，如脂质代谢和心血管疾病，离子通道组织， 多药耐药 我们建立了一个PDZK 1基因敲除小鼠，其特点是增加血浆胆固醇水平 并显著降低SR-BI在肝脏中的表达，导致受损的“胆固醇逆向转运”。 PDZK 1与ARH（常染色体隐性遗传性高胆固醇血症中缺陷基因的产物）一起， 可能是一个不断增长的细胞质衔接蛋白家族，控制细胞的组织特异性活性， 表面受体 最近，我们已经确定，使用转基因小鼠模型，其中截短形式的 PDZK 1基因敲除小鼠的肝脏中PDZK 1过表达，这表明PDZK 1的所有四个PDZ结构域都是必需的。 对于正常的SR-BI表达、定位和功能，尽管单个结构域的精确作用，PDZ 2 尤其是PDZ 4，仍然未知。我们已经确定SR-BI能够与另一个站点交互 在PDZK 1中，除了已知的与PDZ 1的相互作用之外。此外，我们还解决了晶体结构 PDZK 1的第一结构域及其与SR-BI的相互作用。我们还确定PDZK 1是 这表明PDZK 1可能是心血管疾病治疗的有吸引力的靶标。 我们的目标是研究PDZK 1/SR-BI蛋白簇的分子结构。我们将 定义PDZK 1的第二和第四PDZ结构域（PDZ 2和PDZ 4）的功能，并确定它们的 结合伴侣，通过X射线晶体学确定PDZK 1的完整结构，以获得三个 分子的三维结构，并了解PDZK 1如何与其结合伴侣相互作用。我们将 使用转基因小鼠模型将体外获得的结果进行关联，其中改变（突变/截短） PDZK 1转基因将在PDZK 1 KO小鼠的肝脏中表达。这些研究可以提供必要的 背景技术促进胆固醇逆向转运以防止胆固醇代谢的新疗法的开发 形成动脉粥样硬化病变和心肌梗死。

Adaptor, anchoring and scaffolding proteins play an important role in signal transduction. In many situations, the interaction between signaling proteins is mediated by small amino acid sequences binding to specific protein domains, such as src homology (SH), pTyr-binding (PTB) or PDZ domains. These interactions are responsible for determining location, function and activity of receptor and transporter proteins among others. A few years ago, we isolated a novel protein that we named PDZK1. PDZK1 contains four PDZ protein-interaction domains and interacts with the carboxy-terminal portion of a number of membrane associated proteins including the high density lipoprotein (HDL) scavenger receptor SR-BI and several ion channels, one of them involved in multidrug resistance. As a result, PDZK1 is likely to play an important role in biological processes as diverse as lipid metabolism and cardiovascular disease, ion channel organization and multidrug resistance. We generated a PDZK1 knockout mouse which is characterized by increased plasma cholesterol levels and markedly reduced expression of SR-BI in the liver, resulting in impaired "reverse cholesterol transport". PDZK1 joins ARH (the product of the defective gene in autosomal recessive hypercholesterolemia) in what is likely to be a growing family of cytoplasmic adaptor proteins that control the tissue specific activity of cell surface receptors. More recently, we have determined, using a transgenic mouse model in which truncated forms of PDZK1 were overexpressed in the liver of PDZK1 KO mice, that all four PDZ domains of PDZK1 are necessary for normal SR-BI expression, localization and function, although the precise role of individual domains, PDZ2 and PDZ4 in particular, remains unknown. We have determined that SR-BI is able to interact with another site within PDZK1, in addition to the known interaction with PDZ1. In addition, we have solved the crystal structure of the first domain of PDZK1 and its interaction with SR-BI. We have also determined that PDZK1 is atheroprotective, suggesting that PDZK1 may be an attractive target for therapies in cardiovascular diseases. Our objectives are now to study the molecular organization of the PDZK1/SR-BI protein cluster. We will define the functions of the second and fourth PDZ domains (PDZ2 and PDZ4) of PDZK1 and identify their binding partners, define the complete structure of PDZK1 by X-ray crystallography to obtain a three dimensional structure of the molecule and understand how PDZK1 interacts with its binding partners. We will correlate the results obtained in vitro using a transgenic mouse model, where altered (mutated/truncated) PDZK1 transgenes will be expressed in the liver of PDZK1 KO mice. Such studies may provide the necessary background for the development of new therapies promoting reverse cholesterol transport to prevent the formation of atherosclerotic lesions and myocardial infarction.